This invention relates to a portable gas firing apparatus, for cooking, heating, etc.. More particularly, to an apparatus having a gas firing system superposed on a detachable pressure gas cartridge which can be removed for replacement after the gas is consumed.
Portable gas firing apparatus are cooperatively assembled with a box-like container and commonly used by people when going picnic, camping, mountaineering, etc. In U.S. Pat. No. 3,907,490 there is disclosed a kind of gas firing apparatus in which the gas firing system and gas cartridge are respectively disposed inside two chambers divided by a common partition that horizontally passes across a container. The gas firing system can include a burner upwardly extending from the common partition, a control member for gas delivery to the burner, an ignition device, a gas take-off head, etc. The lower bottom portion of the container is constituted by a bowl-like portion which is threadedly attached to an enclosure downwardly extending from the common partition to cooperatively form the lower chamber in which the gas cartridge is held clamped against an annular sealing member of the gas take-off head and kept in a gas-tight connection with the gas take-off head by an upward pressure induced upon full-thread-depth screw action of the bowl-like portion. This screw action not only establishes a gas-tight connection between the gas cartridge and gas take-off head but also forces the top side of the gas cartridge against an axial finger in the form of a sharp spike which is disposed in a slightly projected position in the gas take-off head so that the gas cartridge is perforated by said finger for the excape of the gas to the burner through the gas take-off head.
It has been discovered that gas may leak at the connection between the gas take-off head and the gas cartridge when uncovering the box-like container. A user may wrongly take off the lid by applying a spiral force, instead of by applying an axial pulling force. The spiral force causes the screwed bottom bowl portion to spirally move in a direction departing from the gas take-off head and thereby reduces the upward pressure used to maintain the gas-tight connection.
In some cases, the gas take-off head fails to permit the escape of the gas. The finger may be positioned in a tight fit, relative to the perforation drilled by itself, that will be maintained rigidly at the end of the screw action.